A yakuza boss has been sentenced to death in Japan in what is believed to be a first after his criminal organisation murdered and attacked other citizens.

Satoru Nomura, 74, told the judge Fukuoka District Court, in western Japan, on Tuesday: ‘I asked for a fair decision… You will regret this for the rest of your life,’ Nishinippon Shimbun newspaper reported.

It is believed to be the first time a senior yakuza member has been sentenced to death, the BBC reported.

Nomura, the head of the ‘Kudo-kai’ crime syndicate in southwest Japan, denied accusations he had masterminded the violent assaults. Kudo-kai is often described as Japan’s ‘most violent’ yakuza gang.

According to Japanese broadcaster NHK, there was no direct evidence that Nomura had ordered the attacks.

However, in handing down the sentence, the judge said that the gang operated under such strict rules that it was unthinkable that attacks could have been carried out without its leader’s authorisation.

The trial revolved around attacks carried out by Kudo-kai members between 1998 and 2014. During that time, a former head of a fishing cooperative was shot and killed, and three others – including a nurse and former police officer – were injured by shooting or stabbing.

Autopsies have been ordered to determine the cause of death of each child, a public prosecutor announced on Tuesday, adding that an investigation had been opened into the discoveries.

The autopsies should also make it possible to identify the children’s parents,’ the prosecution said, adding that no hypothesis has been ruled out by investigators.

Technical examinations were carried out at the site, where officers also took statements from the man and other relatives.

BFMTV reported that the man’s wife had died suddenly of cancer on August 10, aged 44, and that he had been clearing the property following her death when he made the discovery.

The couple were childless and the woman had two children from a previous relationship, RTL reported.